Zigzag carbon electric resister.



J. THOMSON.

Patented Nov. 1l, 1919.

)TOEN THOMSON, or NEW YORK, N. Y.

-ZIGZAG CARBON ELECTRIC RESISTER.

Specication of Letters Patent.

Patented Novi 11, 1919.

Application inea october 7, 191s. serial No. 257,216.

To all 'whom it may concern:

Be it known that I, JOHN TiroMsoN, a. citizen of the United States, anda resident `of the borough of Manhattan, city of Newl York, county andState of New York, have invented certain new and useful Improvements inZigzag Carbon Electric Resistere, of which the following is aspeeilicatlon.

'l`he invention particularly relates to zig-zag, carbon, electricresistors for use 1n furnaces. Important objects of the invention are,to so form the resister and so dispose the alternating members whichconnect the zig-zags that a surtace, or surfaces, of the resister willbemaintained at a higher temperature than another surface, or surfaces;and to effect, in a. single carbon body of given lineal dimensions, a'greater resistivity than has hitherto been realizable.

In the drawings,

Figure 1 shows a resister 1n plan;

Fig. 2 is a side elevation thereof;

Fig. 3 is an end elevation, as viewed from the bottom of Figs. l and 2;

Fig. t is a transverse section, as on the line A; and

Fig. 5 is a view similar to Fig. 4 but of modified design.-

The resister, B, is formed as from a carbon bar, whose, originalcross-section would preferably be square, and two of its opposing sidesare planed to angles C, D, forming a. wedge-like cross-section. Thetapered side portions are then nearly entirely separated by forming avertically land longitudinally extending central slot, E, passing fromone end of the barI toward the other end, leaving thereat a relativelynarrow portion, F; The zig-zags are p roduced by cutting alternatingslits, H, which pass crosswise of the said central slot. The slits,H.-extend vertically and transversely. A, part of the. slits'll, extendsdownwardly from the top surlaee of the 'resister toward but short of thebottom surfaceof the resister leaving material, as at h', while theremainder of the slits Hextends upwardly from the bottom surface, towardbut short of the. upper surface of the resister leaving material, as4 ath. In this wise each limb of the bar b 1, ,o||u-sa` distinct resisterconnected in series hy the end-section. or emmeetor, F. The resister, asa whole, thus simulates in its appearance the prongs of a tuning forli',each prong 4having a. similar number of '/.ig-zags. It may also bereferred to as a U-shaped resister each leg of said U-shaped portionhaving a number of-zig-zags. Its separated ends ma be provided withcopper terminals, as I, which are symbolically denoted 'as connected toa poner-circuit, K.

i The object of forming the angular sides is to produce a progressiveincrease of current density, and a corresponding intensity oftemperature. Thus, which is best illustrated by Fig. 4, as"Y theelectric current,

passes from the top, r, to theI bottom s, the cross-sectional area, dueto the, taper, is ronstantly diminishing, where-by the lowersurfaceofthe resister will be the. hotter. This condition can be advantageouslyavailed of in-many cases, as by so setting or disposing theresister'that its hotter portion is presented toward the body to beheated. This effect has been previously realized by the presentapplicant, in the manner shown in his patent of August 8, 1916, No.1,193,633, being therein paiticularly illustrated by Figs. 5, 6 and 7.In that case, however, the increase of current-density is obtained bycausing the current to traverse the connecting portion of a zig-zagalong lines of different lengths, the section traversed by the eurrentbeing uniform, Whilein the present ease the lines of current-traverseare of thesame length but the cross-sectional area progressivelyincreases or decreases.

The. same densitying effect ican lbe attained in a resister which is notcentrally separated, as is shown in F ig. 5, whose sideangles aresharper than in Fig-i. F or example, in this case the maximum increaseof current-density, and the eorreslmmling heating efl'ect along itsbottom surface, would be about 50 per centum greater than along itsupper surface, with a progressive inerezise or decrease'throughout thcmass, as thecase. may be, from one surface to the other.

In the central slotted resister, as shown in the first four figures ofthe drawings, it is in fact a. member`having a compound cireuit formedfrom a monolithic bar or block, possessing the advantages of the utmostcolnpzu-tn-ess, efliciency and endurance.

Obviously, where a wedge-like or other form (if eross-seetion whereby toproduce a progressively increasing or decreasing current-density, wouldnot be advantageous,

a carbon bar of square or rectangular secy tion may be centrallyslottedand crosscuit, having a. restricted sectional area, with slatedin the manner ,hei-ein" described, thereby realizmg'the advantage insingular of obtaining the utmost length of cirthe utmost compactness ofstructure.

What I. claim is:

1.' A zig-zag, carbon, 'electric resister having a longitudinalcentrally disposed slot separating two contiguous series of zig-zags,

the said slot assing from one end of the l carbon bar or lock towardbutnot entirely the other end thereof,

. zig-zag, carbon, electric resister, wedge-like in cross-section, inwhich the slits which produce the zg-zags pass crosswise of the wedge,whereby the area of the connecting portions progressively increases ordecreasesv in the direction traversed by the current.

3. A monolithic, compound, zigzag, carbon, electric resister, formed bya a ,ranged slots that extend vertically and transversely of theresister member.

This sperilicution signed and witnessed this 21st day of August, 198.- i

JOHN THOMSON? Signed in the presence of- RALPH M. THOMSON, H. O. Wmo. y

